Ion exchange resins, commercially used in water purification, are generally prepared commercially by performing chemical reactions, such as sulfonation chloromethylation, on styrene-divinylbenzene copolymers, or other crosslinked vinyl copolymers, in the presence of a halogenated hydrocarbon swelling agent. Halogenated hydrocarbons such as 1,2-dichloroethane, 1,2-dichloropropane and methylene chloride are effective swelling agents for styrene-divinylbenzene copolymers, as more ti11y described in U.S. Pat. Nos. 5,081,160, 2,788,330 and 4,501,526.
Ion exchange resins, currently commercially prepared using halogenated hydrocarbon swelling agents are used in commercial applications which include purifying drinking water, purifying industrial ultrapure water for the power industry, semiconductor industry and other industries and in other industrial applications.
It is anticipated that control of the use of halogenated hydrocarbons may be mandated by regulatory authorities, since under certain conditions halogenated hydrocarbons may have detrimental effects on health or on the environment. Additionally, halogenated hydrocarbons may be corrosive to equipment used in the manufacture of ion exchange resins and may hinder the ability to recycle streams of reactants in the manufacture of ion exchange resins.
Hitherto, halogenated hydrocarbons were used to swell styrene-divinylbenzene copolymers and other crosslinked vinyl copolymers in sulfonation or chloromethylation, in order to attain a high ion exchange capacity (i.e., a high degree of functionalization) and desirable mechanical properties.